Thermal inhibition of repair of methylmethane sulfonate-damaged DNA in chick embryo fibroblasts

Chick embryo fibroblasts were treated with the monofunctional alkylating agent methylmethane sulfonate at various concentrations for 1 h at 42°C, rinsed and then incubated post-treatment at various temperatures at which the kinetics of alkali-labile bond disappearance was followed. Growth experiments showed that these cells grew similarly at temperatures of either 37°C or 42°C. Repair as assessed by removal of alkali-labile bond was also similar for postincubation in the temperature range 37–42°C for damage due to methylmethane sulfonate treatment at concentrations less than 1.5 mM. When the postincubation temperature was raised higher than 42.5–43°C, this type of repair was stopped. The normal internal body temperature of adult chickens is about 41.6°C. Hence the present finding indicates that chick cells are much more severely restricted in DNA repair at temperatures above normal than are mammalian cells, which can function in this respect for several deg. C above 37°C.     

Assessing Greater Sage-Grouse Selection of Brood-Rearing Habitat Using Remotely-Sensed Imagery: Can Readily Available High-Resolution Imagery Be Used to Identify Brood-Rearing Habitat Across a Broad Landscape?

Greater sage-grouse populations have decreased steadily since European settlement in western North America. Reduced availability of brood-rearing habitat has been identified as a limiting factor for many populations. We used radio-telemetry to acquire locations of sage-grouse broods from 1998 to 2012 in Strawberry Valley, Utah. Using these locations and remotely-sensed NAIP (National Agricultural Imagery Program) imagery, we 1) determined which characteristics of brood-rearing habitat could be used in widely available, high resolution imagery 2) assessed the spatial extent at which sage-grouse selected brood-rearing habitat, and 3) created a predictive habitat model to identify areas of preferred brood-rearing habitat. We used AIC model selection to evaluate support for a list of variables derived from remotely-sensed imagery. We examined the relationship of these explanatory variables at three spatial extents (45, 200, and 795 meter radii). Our top model included 10 variables (percent shrub, percent grass, percent tree, percent paved road, percent riparian, meters of sage/tree edge, meters of riparian/tree edge, distance to tree, distance to transmission lines, and distance to permanent structures). Variables from each spatial extent were represented in our top model with the majority being associated with the larger (795 meter) spatial extent. When applied to our study area, our top model predicted 75% of naïve brood locations suggesting reasonable success using this method and widely available NAIP imagery. We encourage application of our methodology to other sage-grouse populations and species of conservation concern.     

Parelaphostrongylus tenuis in New Brunswick: the parasite in white-tailed deer (Odocoileus virginianus) and moose (Alces alces)

Research was initiated in 1983 to investigate the ecology of Parelaphostrongylus tenuis in New Brunswick. The objectives were to determine the prevalence and intensity of infection in white-tailed deer, and to determine whether or not moose feces contained first stage larvae, signifying the completion of the life cycle of P. tenuis in this host. Forty-nine percent of deer pellet samples were positive and 60% of deer heads contained adults of P. tenuis. None of the moose pellet samples contained first stage larvae.     

Behavioral response ofGraminella nigrifrons (Homoptera: Cicadellidae) to experimentally manipulated vibrational signals

Mate recognition for the leafhopper Graminella nigrifrons(Forbes) occurs when a male spontaneously emits a multisectional vibrational calling song to which females respond by emitting simple pulses. Significant differences were found among males in the duration, number of chirps, and chirp rate within sections of the song and the total song. Repeatability (proportion of total variation due to differences among males) of call features ranged from very low (0.04 for total chirps in song) to high (0.67 for section 3 chirp rate). However, song modification and playback experiments revealed that the variation in the measured song features was not important in determining whether a female will respond. Rather, female response depended only on the presence of two of the three types of pulses which comprise a chirp. These essential pulses were found within chirps of all call sections that contain chirps. Manipulation of chirp rates from 0.58 to 2.70 times the normal rate did not affect female response, nor did changing the period of silence between the essential pulse types from 0.25 to 1.75 times the normal period. These results suggest that components of the male calling song function in mate recognition but are not used by females to discriminate among conspecific males.     

Photomovement in Dunaliella salina: Fluence rate-response curves and action spectra

We determined the action spectra of the photophobic responses as well as the phototactic response in Dunaliella salina (Volvocales) using both single cells and populations. The action spectra of the photophobic responses have maxima at 510 nm, the spectrum for phototaxis has a maximum at 450–460 nm. These action spectra are not compatible with the hypothesis that flavoproteins are the photoreceptor pigments, and we suggest that carotenoproteins or rhodopsins act as the photoreceptor pigments. We also conclude that the phototactic response in Dunaliella is an elementary response, quite independent of the step-up and step-down photophobic responses. We also determined the action spectra of the photoaccumulation response in populations of cells adapted to two different salt conditions. Both action spectra have a peak a 490 nm. The photoaccumulation response may be a complex response composed of the phototactic and photophobic responses. Blue or blue-green light does not elicit a photokinetic response in Dunaliella.Diagrams of the optical set-ups used for measuring the responses at the single-cell level and of the plans for building the phototaxometer described in this paper are available to the interested readerWe thank Mr. M. Kubota for a tremendous amount of technical assistance and Mr. R. Nagy for building the phototaxometer. We thank T. Kondo, Professor H. Imaseki and the members of the Laboratory of Biological Regulation, NIBB, for their help and support in various aspects of this research. This research was supported, in part, from grants from the Okazaki Large Spectrograph (Project Nos. 86-535, 87-518, 88-523), the Japanese Society for the Promotion of Science, and the College of Agriculture and Life Sciences at Cornell University to R. W.     

Three theories of stroboscopic motion detection

The three theories derive from three different paradigms. Suprathreshold judgements of perceived quality of motion in multi-flash displays are modelled by space-time Fourier analysis of the motion stimulus. Stroboscopic motion is perceived as being different from real motion to the extent that the additional Fourier components in stroboscopic motion are detectable. Stroboscopic motion of dots along conflicting paths leads to perceptual competition. The theory to describe perceptual I solution derives and proves the uniqueness of strength functions computed only from the time and from the distance between successive points on each path. Time-strength and motion-strength add to determine path-strength; only the strongest path is perceived. Motion-direction detection in continuously drifting two-flash combinations of sinusoidal gratings is described by elaborated Reichardt detectors (ERDs) that compute the covariance of temporal events in two adjacent locations. Other apparently different, detectors that account for direction-detection data are shown to be equivalent to ERDs.     

Effect of indomethacin on proteinuria in rats with autologous immune complex nephropathy

Although non-steroidal anti-inflammatory agents have been used to reduce levels of urinary protein excretion in patients with the nephrotic syndrome, the general usefulness of these drugs in proteinuric states remains unclear. The present study was designed to confirm the efficacy and to investigate some of the mechanism/s of action of non-steroidal anti-inflammatory agents in animals with proteinuria as the result of a single form experimental renal disease. Autologous immune complex nephropathy was produced in groups of Lewis rats by the administration of autologous tubular F×1A antigen. After marked proteinuria developed, indomethacin (8 mg/kg/day) was administered orally to one group of animals for five days while a control group received only vehicle. The level of urinary protein excretion in the indomethacin treated animals was 420 ± 198 mg/day compared to a level of 1180 ± 306 seen in the untreated animals (p < 0.05). When the indomethacin-treated and control animals were compared, the reduction in proteinuria could not be found to be associated with a change in the glomerular filtration rate, urine electrolyte or osmolar excretion rates, electron microscopic appearance of the glomerular basement membrane, or a change in the glomerular permeability to neutral dextran. Treatment of animals with either sodium salicylate or lower doses of indomethacin (both of which resulted also in significant falls in urinary prostaglandin E excretion rates) failed to reduce the levels of proteinuria. Thus, indomethacin was capable of reducing the levels of protein excretion in rats with autologous immune complex nephropathy although the mechanism of action of this agent remains unclear.     

Sulfhydryl Groups in Receptor Binding of Thyrotropin-Releasing Hormone to Rat Amygdala

Abstract: Binding of [³H]-[3-Me-His²]thyrotropin-releasing hormone ([³H]MeTRH) to TRH receptors in rat amygdala was decreased by sulfhydryl reagents in a time-, temperature-, and concentration-dependent manner. A pronounced reduction in receptor density, with little or no change in binding affinity, was apparent following disulfide bond reduction by dithiothreitol (DTT), alkylation of thiol groups by N -ethylmaleimide (NEM), and their oxidation by 5,5'-dithiobis (2-nitrobenzoic acid). Heavy metals (Cd²⁺, Hg²⁺), which complex with reactive -SH residues, also potently inhibited binding. The pharmacological specificity of residual [³H]MeTRH binding in chemically modified amygdala membranes was the same as that in control preparations. Sequential exposure to thiol reagents, in the presence or absence of cations, revealed possible additive effects. Pretreatment of membranes with TRH (10^--⁸-^-10^--⁶ M ), and its continued presence during modification, afforded protection against DTT and NEM. These results indicate the possible importance of thiol groups in the maintenance of TRH receptor conformation.     

Modulation of Receptors for Thyrotropin-Releasing Hormone by Benzodiazepines: Brain Regional Differences

The benzodiazepines (BZDs) chlordiazepoxide (CDE), diazepam (DZM), and flurazepam (FLM) inhibited receptor binding for thyrotropin-releasing hormone (TRH) with low micromolar potency. In contrast, numerous other categories of drugs were previously shown to be inactive. Scatchard analysis of competition data suggested that the BZDs reduced TRH receptor affinity, consistent with competitive inhibition. Receptors from amygdala, retina, and pituitary appeared more sensitive to inhibition by BZDs than those from hypothalamus, hippocampus, spinal cord, or cerebellum. The latter four regions also gave shallower inhibition curves. CDE revealed an apparently biphasic dissociation of [3-Me-His2]TRH([3H]MeTRH) from amygdala membranes at 4 degrees C, with kinetics similar to those with TRH. These results suggest that TRH receptors in the brain are heterogeneous and that certain BZDs in high therapeutic concentrations may exert central effects through actions at TRH receptors or coupled proteins.